青海昆仑河地区含钠闪石硅质岩的发现及其地质意义  

THE DISCOVERY AND GEOLOGICAL SIGNIFICANCE OF RIEBECKITE-BEARING SILICEOUS ROCKS IN KUNLUNHE AREA,QINGHAI PROVINCE

作　　者：陈静 余福承[2] 韩杰[2] 陈健[2] 金婷婷[2] Chen Jing;Yu Fucheng;Han Jie;Chen Jian;Jin Tingting(School of Geographic Sciences Qinghai Normal University Xining,Qinghai 810000,China;Qinghai Geological Survey Institute,Xining,Qinghai 810000,China)

机构地区：[1]青海师范大学地理科学学院,青海西宁810000 [2]青海省地质调查院,青海西宁810000

出　　处：《矿物岩石》2021年第2期52-58,共7页Mineralogy and Petrology

基　　金：国家自然科学基金(41862011);中国科学院“西部之光”人才培养引进计划。

摘　　要：青海昆仑河地区温泉沟脑多金属矿位于东昆仑南坡俯冲增生杂岩带中,是近年来新发现的一处矿点。在考察该矿区过程中,首次在含矿硅质岩中发现了闪石类矿物,且与褐铁矿化或赤铁矿化关系密切。矿区内硅质岩表现出明显的条带状、纹层状构造,并具有典型的热水沉积岩组合--层状硅质岩和重晶石岩组合。硅质岩的岩石地球化学分析表明,5件样品Fe/Ti均大于20,Al/(Al+Fe+Mn)均小于0.35,稀土元素表现出总量低以及北美页岩标准化模式水平或向左倾斜,为典型的热水沉积产物。硅质岩Ce负异常不明显(平均0.90),Lan/Ybn值介于0.31~1.66之间,平均值为1.02,均与大陆边缘地区的范围接近,说明温泉沟脑矿区硅质岩形环境靠近大陆边缘。角闪石矿物学及成分分析表明,氧化物平均含量w(Al2O3)=0.574%,w(FeOT)=25.67%,相应的AlⅣ=0.011,Fe3+=2.067。根据NaB>1.50,(Mg+Fe2++Mn2+)>2.50,以及(Na+K)A<0.50,Mg/(Fe2++Mg)<0.50,AlⅣ<Fe3+,判断该角闪石属于钠闪石。根据钠闪石产出特征及成因分析,认为其形成与后期流体活动有关。钠闪石与褐铁矿化或赤铁矿化几乎相伴产出,结合两者形成的氧化还原环境可以表明该硅质岩中的铁矿化并非前人认为的同生沉积作用形成,可能为后期热液作用产物。The Wenquangounao polymetallic deposit in the subduction accretionary complex belt on the south slope of East Kunlun region, Qinghai Province, which is a newly discovered ore spot in recent years. Amphibole minerals occurred in the ore-bearing siliceous rocks are closely related to limonitization or hematitization. The siliceous rocks in the mining area show obvious banded and laminated structures, and there are typical hydrothermal sedimentary rock assemblages, such as layered siliceous rocks and barite assemblages. Petrogeochemical analysis of siliceous rocks shows that Fe/Ti of the 5 samples are all greater than 20, and Al/(Al+Fe+Mn) are all less than 0.35. The total amount of rare earth elements is low and the normalized model of North America shale is horizontal or left-dipping, characteristic of typical hydrothermal deposits. The negative Ce anomaly of the siliceous rocks is not obvious(average 0.90), and the Lan/Ybn values range from 0.31 to 1.66, with an average of 1.02, which is close to the range of the continental margin area, indicating that the forming environment of siliceous rock in Wenquangounao mining area is close to the continental margin area. Mineralogy and composition analysis of amphibole in the siliceous rock show that the average oxide content of w(Al2O3)=0.574%, w(FeOT)=25.67%, the corresponding AlⅣ =0.011, Fe3+=2.067;and the NaB>1.50,(Mg+ Fe2++Mn2+)>2.50, as well as(Na+K)A<0.50, Mg/(Fe2++Mg)<0.50, AlⅣ<Fe3+, indicating that the amphibole belongs to riebeckite. According to the occurrence characteristics and genetic analysis, the formation of amphibole is related to the later fluid activity. The riebeckite is almost associated with limonitization or hematitization, in accordance with the REDOX environment of their formation, it is considered that the iron mineralization in the siliceous rock is not formed by syngenetic sedimentation as previously thought, but may be the product of late hydrothermal process.

关 键 词：东昆仑南坡 温泉沟脑多金属矿 钠闪石 含矿硅质岩﹔成因 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]